Schmid A, Benz R, Schink B
Lehrstuhl für Biotechnologie, Universität Würzburg, Federal Republic of Germany.
J Bacteriol. 1991 Aug;173(16):4909-13. doi: 10.1128/jb.173.16.4909-4913.1991.
Porins were purified from cells of the anaerobic gram-negative bacterium Pelobacter venetianus grown with 20-kDa polyethylene glycol. After treatment of the cell envelope fraction with sodium dodecyl sulfate-containing solutions, the murein contained only two major peptidoglycan-associated proteins of 14 and 23 kDa. Both proteins were released from the peptidoglycan by the detergent Triton X-100. Genapol X-80 released only the 23-kDa protein. This protein was purified by chromatography on a hydroxyapatite column. It did not form sodium dodecyl sulfate-resistant oligomers. Reconstituted in lipid bilayer membranes, the 23-kDa protein formed cation-selective channels with a single-channel conductance of 230 pS in 1 M KCl. The channel is not a general-diffusion pore, since its conductance depends only moderately on the salt concentration. The channel conducted ammonium much better than potassium or rubidium ions, suggesting that it is probably involved in ammonium uptake. The outer membrane of P. venetianus contains a further, non-murein-associated pore with an unknown molecular mass. It is also cationically selective and has a single-channel conductance of 1.6 nS in 1 M KCl, which suggests that its effective diameter is similar to that of porins from enteric bacteria.
孔蛋白是从以20 kDa聚乙二醇培养的厌氧革兰氏阴性细菌威尼斯佩洛杆菌（Pelobacter venetianus）的细胞中纯化得到的。用含十二烷基硫酸钠的溶液处理细胞包膜组分后，胞壁质仅含有两种主要的与肽聚糖相关的蛋白质，分子量分别为14 kDa和23 kDa。这两种蛋白质都可通过去污剂Triton X-100从肽聚糖中释放出来。Genapol X-80仅能释放23 kDa的蛋白质。该蛋白质通过羟基磷灰石柱层析进行纯化。它不会形成耐十二烷基硫酸钠的寡聚体。在脂质双分子层膜中重组后，23 kDa的蛋白质形成阳离子选择性通道，在1 M KCl中其单通道电导为230 pS。该通道不是一般的扩散孔，因为其电导仅适度依赖于盐浓度。该通道对铵离子的传导能力比对钾离子或铷离子好得多，这表明它可能参与铵的摄取。威尼斯佩洛杆菌的外膜还含有另一种与胞壁质无关的孔，其分子量未知。它同样具有阳离子选择性，在1 M KCl中的单通道电导为1.6 nS，这表明其有效直径与肠道细菌的孔蛋白相似。
